How to interpret statistics Z3

Question

I get the following statistics in Z3.

(:added-eqs            24529
 :binary-propagations  43837
 :bv-bit2core          7115
 :bv-conflicts         156
 :bv-diseqs            10395
 :bv-dynamic-diseqs    10028
 :bv->core-eq          10401
 :conflicts            409
 :decisions            4840
 :del-clause           84926
 :final-checks         2
 :max-generation       4
 :memory               5.69
 :minimized-lits       467
 :mk-clause            88358
 :propagations         90195
 :quant-instantiations 3388
 :restarts             3
 :time                 0.83)

I'd like to know what the metrics used for each result row.

Can you help me?

score 6 · Accepted Answer · edited May 23 '17 at 12:32

6

Disclaimer: I have the feeling that interpreting the statistics the right way is quite an art, and that the Z3 developers are probably the only ones who really know how to do that. Anyway, here is what I know ... or believe:

quant-instantiations indicates the number of instantiated quantifiers. The fewer instantiations the better, but you of course don't want to make your patterns/triggers too strict because Z3 then won't be able to prove anything.

conflicts indicate assignments that happen in the theory subsolvers and that did not make the formula true. If the formula can be satisfied and the number of conflicts is high, it basically means that the prover tried lots of assignments that did not satisfy the formula, i.e., that the prover did not manage to explore the search space in the direction of the goal.

Related questions:

edited May 23 '17 at 12:32

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answered Jul 25 '13 at 14:31

Malte Schwerhoff

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Does the time mean real time or CPU time? – Dingbao Xie Jul 26 '13 at 02:58
@DingbaoXie I don't know, sorry. You could try to find out by checking a complicated formula that takes quite a while to be checked and by giving the Z3 task/process a very low priority. That way it should become apparent which time is measured. – Malte Schwerhoff Jul 26 '13 at 08:17
I dream of a script: it takes a set of benchmarks and tunes Z3 for them. And also says where most of the time goes to. And also hints if the encoding is not efficient! :) – Ayrat Jul 26 '13 at 13:47
@Ayrat Sounds awesome. Please don't hesitate to contact me once your dream has come true :-) – Malte Schwerhoff Jul 26 '13 at 13:53
time is expressed in seconds? – Robert Jul 27 '13 at 02:04
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@Robert Yes, in seconds. – Malte Schwerhoff Jul 29 '13 at 09:34
Memory expressed with that metric? Memory represents the memory consumption by z3? – Robert Jul 29 '13 at 15:52
@Robert I don't know, sorry. The Z3 developers surely do. Should you find out, please post it here. – Malte Schwerhoff Jul 29 '13 at 16:24

How to interpret statistics Z3

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